convert all uses of query to filter

[philvarner]

Related Issue(s):

• Elasticsearch searches should use filter rather than query in most cases #82
• /collection/{c_id}/items should use search method rather than custom code #63

Description:

• Most of the searches were done using query rather than filter. The difference is that query uses scoring to rank results (more like as free-text search), whereas filter does a SQL select style restriction. Filter is faster than query and results can be cached by ES.
• fixed the count to reflect how many items where actually being returned.
• retrieve more than 10 collections now (up to 100)
• consolidate /collections/{c_id}/items logic to use execute_search instead of mostly-duplicated code.
• refactor execute_search to return tuple of items and total result count, since both places where this is called need the count also.

PR Checklist:

• Code is formatted and linted (run pre-commit run --all-files)
• Tests pass (run make test)
• Documentation has been updated to reflect changes, if applicable, and docs build successfully (run make docs)
• Changes are added to the changelog

[jonhealy1]

Looks good